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Trithuria is a genus of small ephemeral Aquatic plant Herbaceous plant that represent the only members of the family Hydatellaceae found in India, Australia, and New Zealand. Kew World Checklist of Selected Plant Families Almost all described species of Trithuria are found in Australia, with the exception of T. inconspicua and T. konkanensis, from New Zealand and India respectively.Dmitry D. Sokoloff, Margarita V. Remizowa, Terry D. Macfarlane, and Paula J. Rudall. 2008. "Classification of the early-divergent angiosperm family Hydatellaceae: one genus instead of two, four new species and sexual dimorphism in dioecious taxa". Taxon 57(1):179-200.Yadav SR, Janarthanam MK. 1995 Trithuria konkanensis (Hydatellaceae), eine neue Art aus Indien. Aqua Planta 20. (3): 91-97 (1995). Until DNA sequence data and a reinterpretation of morphology proved otherwise, these plants were believed to be monocots related to the grasses (Poaceae). They are unique in being the only plants besides two members of Triuridaceae ( Lacandonia schizmatica and L. braziliana) in which the stamens are centred and surrounded by the pistils; in Hydatellaceae the resulting 'flowers' may instead represent condensed inflorescences or non-flowers.
These diminutive, superficially moss-like, aquatic plants are the closest living relatives of a clade comprising two closely related water-lily families Nymphaeaceae and Cabombaceae. Together, these three families compose the order Nymphaeales in the APG III system of flowering plant classification. Trithuria (Hydatellaceae) diverged from the rest of Nymphaeales soon after Nymphaeales diverged from its sister taxon, although the crown clade evolved relatively recently, in the early Miocene (~19 Ma;). The order as a whole is the sister group of all flowering plants except Amborellales.
Trithuria exhibits a remarkable similarity to Centrolepis and species of both genera were mistaken for members of the other genus.Sokoloff, D. D., Remizowa, M. V., Linder, H. P., & Rudall, P. J. (2009). "Morphology and development of the gynoecium in Centrolepidaceae: the most remarkable range of variation in Poales." American Journal of Botany, 96(11), 1925-1940.
The genus consists of tiny, relatively simple plants occurring in Australasia and India. It was formerly considered to be related to the grasses and sedges (order Poales), but has been reassigned to the order Nymphaeales as a result of DNA and morphological analyses showing that it represents one of the earliest groups to split off in flowering-plant phylogeny, rather than having a close relationship to monocots, which it bears a superficial resemblance to due to convergent evolution.
/ref> The diploid chromosome count of the tetraploid species Trithuria konkanensis 2n = 40.Remizowa, M. V., Sokoloff, D. D., Macfarlane, T. D., Yadav, S. R., Prychid, C. J., & Rudall, P. J. (2008). "Comparative pollen morphology in the early‐divergent angiosperm family Hydatellaceae reveals variation at the infraspecific level." Grana, 47(2), 81-100. The diploid chromosome count of Trithuria australis is 2n = 14.Sokoloff, D. D., Marques, I., Macfarlane, T. D., Remizowa, M. V., Lam, V. K. Y., Pellicer, J., … Graham, S. W. (2019). Cryptic species in an ancient flowering-plant lineage (Hydatellaceae, Nymphaeales) revealed by molecular and micromorphological data. TAXON, 68(1), 1–19. doi:10.1002/tax.12026
/ref> by Georg Hans Emmo Wolfgang Hieronymus based on previous work by Ferdinand von Mueller. Mueller had invalidly published the nomen invalidum and nomen nudum Juncella tasmanica in 1854. Juncella tasmanica
/ref> Juncella tasmanica
/ref> Juncella is a nomen illegitimum. In 1904 the genus Hydatella was described by Friedrich Ludwig Emil DielsHamann, U. (1976). Hydatellaceae—a new family of Monocotyledoneae. New Zealand Journal of Botany, 14(2), 193-196. without a type designation, Hydatella
/ref> but the lectotype Hydatella australis has been designated in 2008. The genus Hydatella was synonymised with Trithuria in 2008.
Trithuria was initially placed in the family Centrolepidaceae (now synonymous with Restionaceae ), which is placed in the order Poales Linder, H. P., & Rudall, P. J. (2005). Evolutionary history of Poales. Annu. Rev. Ecol. Evol. Syst., 36(1), 107-124. but it was separated as its own family Hydatellaceae by
/ref> with Hydatella as the type genus. Upon its separation, Hamann stated the new families affinity or placement were still obscure. The correct placement of the family became apparent in 2007, when it was identified as a basal angiosperm lineage. The family Hydatellaceae is now placed in the order Nymphaeales .WFO (2024): Nymphaeales Salisb. ex Bercht. & J. Presl. Published on the Internet;http://www.worldfloraonline.org/taxon/wfo-9000000354. Accessed on: 17 Nov 2024 Alternatively, it is placed in a separate order Hydatellales validly published by James Lauritz Reveal and Alexander Borissowitsch Doweld in 1999 based on previous work by Arthur Cronquist (see the Cronquist system).Doweld A.B. 2022. New names of fossil Nymphaeaceae and allied forms. Geophytology 52(1&2): 1–28.
/ref> This is however not widely accepted, as the order Hydatellales is mostly treated as a synonym of Nymphaeales.
/ref>Reveal, J. L. (2012). An outline of a classification scheme for extant flowering plants. Phytoneuron, 37(1), 1-221.Reveal, J. L., & Chase, M. W. (2011). APG III: Bibliographical information and synonymy of Magnoliidae. Phytotaxa, 19, 71-134.
Species and distribution
Trithuria has at least 13 species, although species diversity in the family has probably been substantially underestimated.
Trithuria inconspicua subsp. brevistyla K.A.Ford - endemic to South Island, New Zealand
Etymology
The generic name Trithuria is derived from the Greek words τρεις treis meaning "three", and θυρις thyris meaning "window". It references the dehiscence of the capsule fruit.
/ref>Department for Environment and Water. (n.d.). Trithuria submersa
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Conservation
The IUCN conservation status of Trithuria lanterna is Least Concern (LC).Brummitt, N. 2013. Trithuria lanterna
Accessed on 13 December 2024. Trithuria inconspicua is critically endangered.Critically endangered Northland lake plant voted NZ'
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External links
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